In the conventional selection circuit for selecting from among a plurality of choices, a round robin circuit is often used as a logic circuit. One example of a selection circuit used for a packet processing apparatus is shown in FIG. 13. In particular, a selection circuit 100 shown in FIG. 13 includes a round robin circuit 102, which in turn sequentially selects and outputs the packets stored in four queues 101.
In recent years, a great number of queues have come to be used in a packet processing apparatus to realize features such as a band control function. The selection circuit used for selection of these queues is required to rapidly select from among a multiplicity of choices. To meet this requirement, a selection circuit is known, in which a plurality of round robin circuits are connected to each other through a loop-like search path. Each round robin circuit is controlled by a control unit, for example as disclosed by Japanese Unexamined Patent Publication No. 2003-179632.